Field of the Invention
Embodiments of the present invention generally relate to soles and articles of footwear having soles, and more particularly relate to an article of footwear having projections extending from a sole of the article of footwear.
Background Art
Individuals are often concerned with the amount of flexibility and cushioning an article of footwear provides, as well as the aesthetic appeal of the article of footwear. This is true for articles of footwear worn for non-performance activities, such as a leisurely stroll, and for performance activities, such as running, because throughout the course of an average day, the feet and legs of an individual are subjected to substantial impact forces. When an article of footwear contacts a surface, considerable forces may act on the article of footwear and, correspondingly, the wearer's foot. The sole functions, in part, to cushion the wearer's foot and to protect it from these forces. To achieve adequate cushioning, many footwear soles are relatively thick and heavy, which can greatly reduce the flexibility of the sole. When sole size and/or weight are reduced to achieve other performance goals, protection of the wearer's foot is often compromised.
The human foot is a complex and remarkable piece of machinery, capable of withstanding and dissipating many impact forces. The natural padding of fin at the heel and forefoot, as well as the flexibility of the arch, help to cushion the foot. An athlete's stride is partly the result of energy which is stored in the flexible tissues of the foot. For example, a typical gait cycle for running or walking begins with a “heel strike” and ends with a “toe-off”. During the gait cycle, the main distribution of forces on the foot begins adjacent to the lateral side of the heel (outside of the foot) during the “heel strike” phase of the gait, then moves toward the center axis of the foot in the arch area, and then moves to the medial side of the forefoot area (inside of the foot) during “toe-off”. During a typical walking or running stride, the Achilles tendon and the arch stretch and contract, storing and releasing energy in the tendons and ligaments. When the restrictive pressure on these elements is released, the stored energy is also released, thereby reducing the burden which must be assumed by the muscles.
Although the human foot possesses natural cushioning and rebounding characteristics, the foot alone is incapable of effectively overcoming many of the forces encountered during every day activity. Unless an individual is wearing shoes which provide proper cushioning and support, the soreness and fatigue associated with every day activity is more acute, and its onset accelerated. The discomfort for the wearer that results may diminish the incentive for further activity. Equally important, inadequately cushioned footwear can lead to injuries such as blisters; muscle, tendon and ligament damage; and bone stress fractures. Improper footwear can also lead to other ailments, including back pain.
Proper footwear should complement the natural functionality of the foot, in part, by incorporating a sole (typically including an outsole, midsole and insole) which absorbs shocks. Therefore, a continuing need exists for innovations in providing cushioning to articles of footwear.